Pallets have assumed an indispensable place in product storing and transferring in many industries. Traditionally pallets are made up of wood, weighing at least 50 kg. each with an average life span of 6–9 months. These pallets during the industrial rigors of rough handling, chip off, break down, expose the nails which would tear off the bags leading to the generation of sweep-off grade (polymer granules) materials. During rainy seasons, if wooden pallets get wet with water, resulting in weakening of their performance and reduction in their life span. Wood is also a good substrate for the growth of fungus and bacteria, especially under moist conditions, which is a severe disadvantage. The nails used in the pallets tend to rust and can cause cargo damage or injuries.
With the increasing environment responsibility, wooden pallets are gradually discouraged and may be eventually discarded. Attempts to form pallets from other materials in order to avoid the disadvantages inherent in wooden pallets have been only partially successful. Metallic pallets, which were once considered to be ready alternatives for wooden pallets, were soon found to be unwieldy, inconvenient and even unsafe, because of their heavy weight and tendency to cause noise while in use in bagging sections. Accordingly, metallic pallets are gradually becoming unacceptable in the industry.
Plastic pallets, both thermoset as well as thermoplastic, made their modest entry into this high demanding, rough and tough application. The plastic pallet performance is influenced mainly by two factors 1) the performance properties of the pallet material and 2) the design of the pallet. The thermoset pallets, particularly the FRP pallets, chip off during use and bend heavily under load (of nearly 2 tons) leading to problems for entry of forklift. Hence these too are unacceptable and are discouraged. Thus, there is an urgent need for a thermoplastic pallet capable of meeting the demands of the industry. It is also desirable that pallets meet the long-term investment value such as cost-per-use and life cycle considerations. Thus, there is an immediate need for a pallet design comprising a plastic material that overcomes the disadvantages of the prior art. It is desirable, specifically, to provide a pallet that is inexpensive and relatively light in weight but yet strong, and which is formed of recyclable material, stackable, capable of being assembled on site, capable of being picked up by a fork lift, resistant to the growth of fungus and bacteria, and capable of being easily cleaned whenever required.
Several attempts have been made for developing load bearing thermoplastic pallets. U.S. Pat. No. 5,955,546 (1999) issued to Bates et al., describes a process for preparing melt-miscible polyolefin blends of two or more polyolefins. U.S. Pat. No. 5,861,463 (1999) and U.S. Pat. No. 6,140,420 (2000) issued to Sehanobish et al., describe methods for making melt processable impact-modified thermoplastic compositions and articles fabricated therefrom. Another U.S. Pat. No. 5,404,829 (1995) issued to Shuert, provides a design for rackable plastic pallet with an upper plastic platform and lower plastic base interconnected by leg or strut structures. Another U.S. Pat. No. 6,123,032 (2000) issued to Ohenesian, describes an improved load bearing pallet including at least an upper deck formed of a sheet preferably of plastic with a load engaging surface on one side of the sheet and a lift engaging surface on the other. In another U.S. Pat. No. 6,138,532 (2000) issued to Fujii et al., a synthetic resin pallet and manufacturing method therefor was described. And yet in another U.S. Pat. No. 6,125,770 (2000) issued to Bradenburg, a load-bearing plastic pallet with optional reinforcement members, which reduce a flexure of the pallet deck, was illustrated.